A gene dysfunction module reveals the underlying pathogenesis of hidradenitis suppurativa: An update

Hidradenitis Suppurativa Cancer Risk: A Review of the Literature

Background

This systematic review explores the increased cancer risk in patients with hidradenitis suppurativa (HS), particularly cutaneous squamous cell carcinoma (SCC) and lymphoma. Chronic inflammation and immune dysregulation in HS are identified as key factors contributing to malignant transformation, often observed in areas of prolonged tissue damage.

Objectives and Results

The NOTCH signaling pathway, disrupted by smoking, plays a dual role in cancer, acting as both a tumor suppressor and a proto-oncogene depending on the context. Mutations in NOTCH and TP53 are common in SCC linked to HS, with a prevalence of 0.5% to 4.6%, predominantly in men and localized to the buttock and anogenital regions. Histological analyses suggest that malignant transformation occurs within keratinized epithelium, supported by altered cytokeratin expression. Immune dysregulation in HS-affected areas, compounded by scarring and lymphatic disruption, further exacerbates tumorigenic potential. While anti-TNF-alpha therapies have been implicated in cancer risk, conflicting evidence and meta-analyses suggest no consistent increase in non-melanoma skin cancers (NMSC). Similarly, IL-17 inhibitors show potential risks but lack robust evidence in HS-specific populations.

Conclusion

In conclusion, HS-associated malignancies, particularly SCC, underscore the need for further research to elucidate the mechanisms linking chronic inflammation to cancer development. Insights from such studies could guide preventative and therapeutic strategies, improving outcomes for HS patients.

Essentials of hidradenitis suppurativa: a comprehensive review of diagnostic and treatment perspectives

Hidradenitis suppurativa, or acne inversa, is a chronic inflammatory skin condition with recurrent inflammatory nodules, abscesses, subcutaneous tracts, and scars. This condition may cause severe psychological distress and reduce the quality of life for affected individuals. It is considered to have one of the most damaging effects on quality of life of any skin disorder as a result of the discomfort and foul-smelling discharge from these lesions. Although the pathophysiology of HS is still unclear, multiple factors, including lifestyle, genetic, and hormonal factors, have been associated with it. The pathogenesis of HS is very complex and has wide clinical manifestations; thus, it is quite challenging to manage and often requires the use of combination treatments that must be tailored according to disease severity and other patient-specific factors. Although lifestyle changes, weight loss, quitting smoking, topical treatments, and oral antibiotics are adequate for mild cases, the challenge for healthcare professionals is dealing with moderate-to-severe HS, which often does not respond well to traditional approaches. This literature review, consisting of an overview of the various assessment tools and therapy strategies available for the diagnosis and treatment of HS from published literature, aims to be a guide for practicing clinicians in dealing with the complexities associated with this disease.

The Pathogenesis and Treatment of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a multifactorial disease involving the skin and subcutaneous tissues characterized by deep-seated, painful nodules and abscesses with draining sinus tracts. It affects mostly younger individuals between the ages of 18 and 34. The discomfort and embarrassment that patients affected by HS experience negatively impact their daily lives. It is associated with decreased quality of life and high rates of comorbid depression and anxiety. The rate of depression in HS was reported to be as high as 26%. Its pathogenesis is multifactorial and as such requires a multimodal approach to treatment, which subsequently is reviewed here. Moreover, the pathogenesis of HS is complex and only partially understood. Autoinflammation is the key driver of disease development and is linked with dysregulated inflammasome activation with the subsequent production of inflammatory cytokines. Genetics and cutaneous microbiome play a role in the development of chronic inflammation and lesion formation. Risk factors such as obesity, metabolic syndrome, diabetes, and smoking also add to the systemic inflammation. Targeting these risk factors is a key aspect of the treatment of HS. Lifestyle modifications are used in conjunction with pharmacotherapy and procedures to effectively manage the disease.

The genetic aspects of hidradenitis suppurativa

Genetic aspects have a substantial role in hidradenitis suppurativa (HS) pathogenesis. A positive family history of HS occurs in about one-third of HS cases and is significantly higher in patients with early onset of the disease. Recent twin studies have shown a high heritability in HS, fortifying the importance of genetic factors in disease pathogenesis. Based on existing knowledge on the genomics of HS, the disease can be categorized as familial HS, sporadic, syndromic HS, and "HS plus" associated with other syndromes. In familial HS, autosomal dominant transmission is proposed, and monogenic inheritance is rare. This monogenic trait is related to mutations of γ-secretase component genes and Notch signaling or defects in inflammasome function. With newly discovered gene mutations, such as those related to innate and adaptive immunity, skin microbiome, inflammasome, epidermal homeostasis, and keratinization pathway, we can define HS as a polygenic, multifactorial, autoinflammatory disease. To fully elucidate the genetic aspects of HS, we need extensive, long-term global collaborations.

Autoantibodies Present in Hidradenitis Suppurativa Correlate with Disease Severity and Promote the Release of Proinflammatory Cytokines in Macrophages

Hidradenitis suppurativa (HS), also known as acne inversa, is a debilitating inflammatory skin disorder that is characterized by nodules that lead to the development of connected tunnels and scars as it progresses from Hurley stages I to III. HS has been associated with several autoimmune diseases, including inflammatory bowel disease and spondyloarthritis. We previously reported dysregulation of humoral immune responses in HS, characterized by elevated serum total IgG, B-cell activation, and antibodies recognizing citrullinated proteins. In this study, we characterized IgG autoreactivity in HS sera and lesional skin compared with those in normal healthy controls using an array-based high-throughput autoantibody screening. The Cy3-labeled anti-human assay showed the presence of autoantibodies against nuclear antigens, cytokines, cytoplasmic proteins, extracellular matrix proteins, neutrophil proteins, and citrullinated antigens. Most of these autoantibodies were significantly elevated in stages II‒III in HS sera and stage III in HS skin lesions compared with those of healthy controls. Furthermore, immune complexes containing both native and citrullinated versions of antigens can activate M1 and M2 macrophages to release proinflammatory cytokines such as TNF-α, IL-8, IL-6, and IL-12. Taken together, the identification of specific IgG autoantibodies that recognize circulating and tissue antigens in HS suggests an autoimmune mechanism and uncovers putative therapeutic targets.

[Pathogenesis of hidradenitis suppurativa/acne inversa]

Hidradenitis suppurativa/acne inversa (HS) has a multifactorial pathogenesis. In addition to a sporadic form, a familial form is reported in around 40% of patients, for whom an autosomal dominant (AD) inheritance with reduced gene penetrance is assumed. The phenotype of the disease with inflammatory nodules, abscesses and secreting sinus tracts suggests an infectious origin, but the exact role of the bacteria detected in HS pathogenesis remains unclear. Smoking and metabolic syndrome are regarded as important trigger factors in HS, with obesity and hormonal changes playing a pathogenic role in the latter. Ultimately, Toll-like receptors, antimicrobial peptides, immune cells and key cytokines are involved in the excessive inflammatory reaction of HS and are also the targets of future therapies.

Cutaneous Squamous Cell Carcinoma in Patients with Hidradenitis Suppurativa

Background: Cutaneous squamous cell carcinoma (cSCC) is a rare complication of hidradenitis suppurativa (HS). Objectives: To conduct a systematic review and an individual patient data (IPD) meta-analysis to describe the clinical characteristics of HS patients developing cSCC and determine predictors of poor outcome. Methods: Medline/PubMed, Embase, and Web of Science were searched for studies reporting cSCC arising in patients with HS from inception to December 2019. A routine descriptive analysis, statistical hypothesis testing, and Kaplan-Meier survival curves/Cox proportional hazards regression models were performed. Results: A total of 34 case reports and series including 138 patients were included in the study. The majority of patients were males (81.6%), White (83.3%), and smokers (n = 22/27 reported) with a mean age of 53.5 years. Most patients had gluteal (87.8%), Hurley stage 3 HS (88.6%). The mean time from the diagnosis of HS to the development of cSCC was 24.7 years. Human papillomavirus was identified in 12/38 patients tested. Almost 50% of individuals had nodal metastasis and 31.3% had distant metastases. Half of the patients succumbed to their disease. Conclusions: cSCC is a rare but life-threatening complication seen in HS patients, mainly occurring in White males who are smokers with severe, long-standing gluteal HS. Regular clinical examination and biopsy of any suspicious lesions in high-risk patients should be considered. The use of HPV vaccination as a preventive and possibly curative method needs to be explored.

Immunopathogenesis of hidradenitis suppurativa and response to anti-TNF-α therapy

Hidradenitis suppurativa (HS) is a highly prevalent, morbid inflammatory skin disease with limited treatment options. The major cell types and inflammatory pathways in skin of patients with HS are poorly understood, and which patients will respond to TNF-α blockade is currently unknown. We discovered that clinically and histologically healthy appearing skin (i.e., nonlesional skin) is dysfunctional in patients with HS with a relative loss of immune regulatory pathways. HS skin lesions were characterized by quantitative and qualitative dysfunction of type 2 conventional dendritic cells, relatively reduced regulatory T cells, an influx of memory B cells, and a plasma cell/plasmablast infiltrate predominantly in end-stage fibrotic skin. At the molecular level, there was a relative bias toward the IL-1 pathway and type 1 T cell responses when compared with both healthy skin and psoriatic patient skin. Anti-TNF-α therapy markedly attenuated B cell activation with minimal effect on other inflammatory pathways. Finally, we identified an immune activation signature in skin before anti-TNF-α treatment that correlated with subsequent lack of response to this modality. Our results reveal the fundamental immunopathogenesis of HS and provide a molecular foundation for future studies focused on stratifying patients based on likelihood of clinical response to TNF-α blockade.

In silico Analysis of Gamma-Secretase-Complex Mutations in Hidradenitis Suppurativa Demonstrates Disease-Specific Substrate Recognition and Cleavage Alterations

Background: Familial Hidradenitis Suppurativa and Familial Alzheimer's Disease are both associated with Gamma-Secretase Complex mutations; however, the two diseases are not epidemiologically associated. Understanding the molecular differences between the two diseases may aid in the development of hypotheses for differing pathogenesis and ultimately, targets for detection. Aims: To characterize the in silico structural and functional alterations to the Gamma Secretase Complex in documented mutations in Familial Hidradenitis Suppurativa, along with comparison of downstream substrate recognition and cleavage. Methods: In silico analysis of publicly available genomic data, assessment of protein structure and binding affinity using Swiss-model and Dynamut was undertaken. Differential Expression was expressed using Log Fold Change using the general framework for linear models in R. Differentially expressed genes (DEGs) were defined by FCH ≥1.5 or ≤-1.5 and false discovery rate (FDR ≤ 0.05). Results: Twenty three of 39 mutations in HS are degraded via nonsense mediated decay with altered substrate and binding affinity of substrates identified in the remaining mutations. Significant differential expression of ErbB4, SCNB1, and Tie1 in lesional skin was specific to Hidradenitis Suppurativa and EphB2, EPHB4, KCNE1, LRP6, MUSK, SDC3, Sortilin1 in blood specific to Familial Alzheimer's Disease. Discussion and Conclusions: We present the first in silico evidence as to the impact of documented mutations in Familial Hidradenitis Suppurativa. We also demonstrate unique substrate recognition and cleavage between Hidradenitis Suppurativa and Familial Alzheimer's Disease, providing a potential explanation as to why the two diseases do not occur within the same pedigree. These proteomic signatures may be a first step in identifying reliable biomarkers for Familial Hidradenitis Suppurativa.